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Biomedical subjects

J Ring

Publications and source records attributed to J Ring.

At least 289 records · Page 16Linked to original sources
PubMed1997

Quantitative determination of pentaerythrityl tetranitrate and its metabolites in human plasma by gas chromatography/mass spectrometry.

Up to now, there has been no data available on the pharmacokinetics of pentaerythrityl tetranitrate (PETN, CAS 78-11-5) and its metabolites, pentaerythrityl-trinitrate (PE-tri-N), pentaerythrityl-dinitrate (PE-di-N), pentaerythrityl-mononitrate (PE-mono-N) in human plasma. Therefore, in order to determine PETN and its metabolites in plasma sensitive and highly selective GC/MS methods had to be developed and validated. PETN and its metabolite PE-tri-N were validated in the concentration range 50 pg/ml to 10 ng/ml. Isosorbide dinitrate (ISDN) was used as the internal standard and the analytes were extracted with dichloromethane from the plasma. The mass spectrometric tests were carried out using chemical ionization in the negative mode (NlCl) with the application of ammonia as a reagent gas. The nitrate ion m/z 62 was determined in the analytes and internal standard. The accuracy of the mean of the quality control samples during the three days (between days) was between 100 and 110% (PETN), as well as 90 and 106% (PE-tri-N). After an oral application of 100 mg PETN in a pilot study, unchanged PETN and PE-tri-N was measured in plasma. Both metabolites PE-di-N and PE-mono-N were validated at the concentration range of 0.25 ng/ml to 25 ng/ml plasma. After extraction, these analytes were derivatized with BSTFA (N,O-bis[trimethylsilyl]trifluoro-acetamide). The applied internal standard was isosorbide-5-mononitrate (IS-5-MN). The mass spectrometric tests were carried out in the same manner as for PETN and PE-tri-N with chemical ionization in the NlCl mode. The detected masses were m/z 324 for PE-di-N, m/z 351 for PE-mono-N and m/z 217 for IS-5-MN. The accuracy of the mean of the quality control samples during 5 days were between 104 and 107% (PE-di-N) and 102 and 106% (PE-mono-N). The maximum concentration of these analytes in the subject samples were on the average all over 5 ng/ml plasma after the oral administration of 100 mg PETN.

Calibration↗
PubMed1997

Skin testing of the pruritogenic activity of histamine and cytokines (interleukin-2 and tumour necrosis factor-alpha) at the dermal-epidermal junction.

Cytokines have been proposed as histamine-independent itch mediators. To investigate this hypothesis, single doses of interleukin-2 (IL-2, 10 MU/mL) and tumour necrosis factor alpha (TNF-alpha, 10 micrograms/mL) were delivered to the epidermis of 10 healthy volunteers with a controlled skin-prick model; 1% histamine and solvent controls were included in a double-blind, randomized crossover design. Itch ratings (computerized visual analogue scale) were obtained every 20 s for 15 min and cutaneous reactions (weal, flare and temperature) were measured. Reactions were also recorded after 2, 24 and 48 h. The mean itch ratings were: histamine 35.5, IL-2 3.3 (both P < 0.01 compared with control), TNF-alpha 1.6 and solvent control 1.75 (not significant). Weal and flare occurred only with histamine. In two volunteers, an inflammatory papule with transient pruritus developed 12-18 h after applying IL-2. In conclusion, IL-2 showed a rapid, low pruritogenic effect, which may be followed by an inflammatory response. TNF-alpha induced no itching in this setting. Skin-prick testing with appropriate doses of potential pruritogens provides a safe and sensitive model for further chemoreceptor studies.

Adult↗
PubMed1997

Melanoma-associated paraneoplastic retinopathy: case report and review of the literature.

A 51-year-old white male suffering from metastatic malignant melanoma of the skin presented with lymph node metastases and paraneoplastic retinopathy 4 years after resection of the primary tumour. There were no cerebral metastases. Ocular symptoms consisting of night blindness and sensations of 'shimmering lights' persisted after total resection of the inguinal lymph node metastases and administration of dacarbazine and prednisone. Perimetry of both eyes was abnormal with concentric restriction. Electroretinography showed significantly reduced amplitudes in both eyes. Only 11 patients with melanoma-associated retinopathy (MAR) have been described. High titres of autoantibodies against whole retina extract were detected by enzyme-linked immunosorbent assay (ELISA) reactions. Indirect immunohistochemistry showed strong autoantibody activity against retinal bipolar cells.

Autoantibodies↗
PubMed1996

Correlations between histamine-induced wheal, flare and itch.

Correlations between the skin reactions wheal and flare and the subjectively reported degree of itch were investigated in response to 1% histamine, intradermally applied by standardized skin prick and by iontophoresis. Experiments were performed with 15 male volunteers using a threefold repeated measures design (skin prick, and iontophoresis with 0.13 mA for 10 s and with 2.0 mA for 10 s). Skin reactions (perpendicular diameters) were determined at the time of their maximum (10 min). Itch was rated on a computerized visual analogue scale which was anchored upon the individual scratch threshold. Most effective in producing itch was the skin prick which caused strong sensations markedly above the scratch threshold during the entire period of measurement (30 min), whereas iontophoresis induced only transient itch sensations. On the other hand, the largest wheals were generated by iontophoresis of both intensities (mean 10 or 14 mm vs 6 mm with skin prick). The higher current induced higher itch, wheal and flare responses, but after eliminating this effect of stimulus intensity, no correlations were found. In contrast, skin prick-induced flare reactions varied with the degree of itch above the scratch threshold (r = 0.56; P < 0.01). Repeated measurements showed a higher stability for the itch reaction with skin prick compared with iontophoresis. It is hypothesized that in iontophoresis the brief (10-s) histamine bolus passed the most superficial pruritoceptive C fibres too quickly to induce long-lasting itch sensations, whereas the skin prick caused a deposit at the dermal-epidermal junction releasing histamine during the entire time of measurement. Consequently, both the C fibre-mediated itch and the axon reflex flare were more pronounced with the skin prick, and the wheal resulting from a permeability increase in the postcapillary venule walls was an independent phenomenon.

Adult↗
PubMed1996

Autoradiographic mapping of beta-adrenoceptors in human skin.

A high density of beta 2-adrenoceptors has been found in human skin. Using autoradiographic mapping we investigated the distribution of beta 1- and beta 2-receptors in normal and diseased human skin. Cryostat sections of human skin obtained at biopsy were incubated with [125I]-iodocyanopindolol and nonspecific binding was identified by incubation of adjacent sections with 200 microM (-)-isoproterenol; beta 2-receptors were visualized using CGP 20712A and beta 1-receptors using ICI 118,551 as competing agents. The epidermis was densely labelled with an even distribution throughout all layers. Most of the beta-receptors were of the beta 2-subtype, with practically no beta 1-receptors. beta-Receptors were also localized to eccrine sweat glands, dermal blood vessels, and perivascular inflammatory cells, but there was no labelling of sebaceous glands. Topical glucocorticoids caused an increase in the density of epidermal beta-receptors. We conclude that keratinocytes and eccrine sweat glands express high densities of beta 2-receptors, suggesting that they may have a physiological role in the regulation of these cells.

Autoradiography↗
PubMed1996

[Induction of multiple melanocytic nevus cell nevi in 2 children with malignant hematologic systemic diseases and chemotherapy-induced immunosuppression].

Two children developed multiple melanocytic naevi after polychemotherapy administered for acute lymphoblastic leukaemia in one and for non-Hodgkin lymphoma in the other. Induction of naevi does not seem to be related to specific agents used in chemotherapy, but rather to the immunosuppression resulting from multiple-agent chemotherapy. There are reports in the literature of both intrinsically and iatrogenically immunosuppressed patients who have developed multiple melanocytic naevi.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

[Parry-Romberg syndrome. Summary and new knowledge based on an unusual case].

A 52 year old female with Parry-Romberg syndrome presented with gradual atrophy of the subcutaneous fat and muscle on her chest and back. The disease process was limited to the C3 to T2 dermatomes on the right side. In addition, there was muscle atrophy of the right arm and extending down the back to T10, als well as right sided paralysis of the diaphragm. Sympathetic nerve blockage reduced pain and hyperesthesia; no progression was seen over several months using NMR to monitor the patient. The Parry-Romberg syndrome has been defined in many ways; in view of this unusual case, we review the literature, attempting to provide a more accurate case definition.

Adipose Tissue↗
PubMed1996

[Treatment of atopic eczema in interdisciplinary cooperation between dermatology and psychosomatic medicine. An individual case report].

Atopic eczema is one of the most frequent dermatological diseases, with a still increasing incidence. Although its etiopathogenesis is still not completely understood, a variety of triggering factors are known. The following case report describes the clinical course of atopic dermatitis in a 2-year-old boy in whom both IgE-mediated allergic reactions and psychological factors were involved in triggering and maintenance of skin lesions. This demonstrates how important both dermatological therapy and close cooperation with the field of psychosomatic medicine can be.

Child, Preschool↗
PubMed1996

Immunoreactivity of glycoprotein IIb is present in metastasized but not in non-metastasized primary malignant melanoma.

Glycoprotein IIb-IIIa (integrin alpha IIb beta3) is an adhesive receptor involved in platelet aggregation and adhesion to the extracellular matrix. Previous studies showed the presence of IIb-IIIa-like glycoproteins on cells of melanoma cell lines and on cells of lymph node metastases. This study evaluates the presence of glycoprotein IIb-IIIa subunits on cells of primary cutaneous malignant melanomas with (n = 4) and without (n = 9) metastases over a period of 6 years and on naevus cells (n = 4). Monoclonal antibodies directed against the subunits of the glycoprotein IIb-IIIa receptor were used on paraffin-embedded sections and evaluated by means of immunohistochemistry. The glycoprotein IIb subunit was exclusively present on cells of metastatic melanomas. It was not found on non-metastatic melanomas or benign melanocytes. These data favour the role of the integrin receptor glycoprotein IIb-IIIa in the metastatic behaviour of malignant melanomas.

Adult↗
PubMed1996

Consensus radiation protection practices for academic research institutions.

Under the auspices of the Howard Hughes Medical Institute, a set of consensus guidelines for Radiation Protection Practices has been developed for biomedical research using radioactive materials. The purposes of the guidelines are (1) to promote good radiation protection practices consistent with the needs of biomedical research, the ALARA principle, and regulatory requirements; (2) to establish common goals and consistent practices within radiation safety programs; and (3) to build a meaningful partnership between radiation safety professionals and the biomedical research community. These practices are intended to enhance radiation protection and the efficiency of the research staff. The consensus guidelines will lessen the variability in radiation safety practices that is evident among many academic research institutions and will encourage better acceptance and regulatory compliance by users of radioactive materials in biomedical research.

Academies and Institutes↗
PubMed1996

Atopic eczema and other manifestations of atopy: results of a study in East and West Germany.

Within an environmental health study, dermatologic examination of 1273 pre-school-age children (5-7 years old) was carried out in selected areas of East (n = 287) and West (n = 987) Germany in spring 1991. On the basis of comparable genetic background, the influence of a different exposure to air pollutants on the manifestation of atopic diseases was investigated. Halle an der Saale (East Germany) and Duisburg (North/South) as well as Essen (West Germany) were chosen as polluted study areas, whereas the countryside town of Borken (West Germany) served as a control region. Outdoor pollution with particles and SO2 was significantly higher in Halle an der Saale. Of the total study group, 12.9% suffered from atopic eczema at the time of examination. The prevalence was highest in East Germany (17.5%; adjusted odds ratio [OR] 1.39, confidence intervals [GI] 0.77-2.52, compared to Borken). The reported frequencies of hay fever and asthma in the total study population were 2% and 1.3%, respectively, without significant differences between study sites. Some 34.7% of the children showed at least one positive skin prick test reaction; significantly (P < 0.001) higher sensitization rates were obtained in western regions (Essen, Duisburg-South) than in the control region (Borken) and East Germany. Multivariate analysis of the prevalence of atopic eczema showed associations with parental predisposition (OR 1.52, CI 1.03-2.25), sex (for boys, OR 0.63, CI 0.43-0.92), location (Duisburg-South vs Borken OR 0.52, CI 0.30-0.96), month of investigation (May vs April, and March vs February OR 0.55, CI 0.37-0.81), contact with rabbits (for girls, OR 2.90, CI 1.36-6.19), animal fur in bedrooms (2.17, 1.01-4.67), indoor use of gas without hood (1.68, 1.11-2.56), and distance of homes from a busy road (< 50 m 1.71, 1.07-2.73). Nonsignificant associations were observed for history of helminthic infections (OR 1.61, CI 0.98-2.64) and high parental education level (OR 1.83, CI 0.83-4.02). In East and West Germany, atopic eczema seems to follow a course different from that of respiratory allergic diseases and specific sensitization, a fact which underlines the need for a differentiated analysis.

Air Pollutants↗